Research

Flow in porous media

Watering a plant is an everyday choir we do without seeing the complexity in it, probably since it is not a lot of water so we can water some more. But what if we have a field of plants we need to irrigate and not enough water, then we should really optimize our irrigation. For that, we need to understand the complex physics behind flow in porous media.

On the Deformation of Artificial Rocks Due to Fluid Injection

Arnold Bachrach

Pressurized fluid injection into underground rocks occurs in applications like carbon sequestration, enhanced geothermal energy production, wastewater disposal and hydraulic fracturing, and may lead to human-induced earthquakes and surface uplift. The fluid injection raises the pore pressure within the porous rocks, while deforming them, yet this coupling is not fully validated for risk assessment as experimental studies of rocks are usually limited to postmortem inspection and cannot capture the complete deformation process in time and space.

We investigate injection-induced deformation of a unique rock-like medium mimicking the deformation of sandstone, yet under low pressure. We create this unique medium by sintering plastic particles at the size of sand grains. We incorporate and solidify about 1% fluorescent particles within the sample to track the local deformation. The tracking is achieved by saturating the sample with oil (immersion liquid) that has similar optical properties as the plastic particles, transforming the artificial rock from opaque to transparent, apart from the fluorescent particles that fluoresce. We then inject the same oil at higher and higher pressure through the artificial rock while measuring the injection pressure and capturing the fluorescent particles movement by using a high-resolution fast camera. Because the fluorescent microspheres are part of the material structure their movement represent the internal deformation of the medium. Then, we quantify the fluorescent particle movement by using image analysis software (PIVlab 2.5).

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Exploring the Impact of Heterogeneity and Flow Rate on Mixing and Displacement of Miscible Phases in Porous Media

Eliyahu-Yakir Yahel

Miscible phase flow in porous media plays a significant role in many natural and industrial processes, such as CO2 sequestration, aquifer salinization, and soil pollution. In these processes, a less dense and less viscous invading phase mixes with a more dense and viscous defending phase at the interface between the two phases. In this research, we address the gap between the pore scale and volume scale by examining how the inner structure of the porous medium, or heterogeneity, leads to various mixing patterns for different inlet pressures and heterogeneity levels. We will use a low-viscosity fluid invading and mixing with a high-viscosity fluid in a 2D porous media at various flow rates and heterogeneity levels to investigate the impact on fingering patterns and displacement to mixing patterns. Our results will show that these variations in displacement to mixing have a unique signature at the Darcy scale as measured by flux measurements, demonstrating that the pore scale phenomenon for miscible phase flow in porous media can propagate to the Darcy scale.

Applying Thermodynamic Framework to Analyze the Reaction-Transport Interaction in the Porous Media at Varying Peclet Number: Entropy, Enthalpy, Heterogeneity

Evgeny Shavelzon

Dissolution and precipitation processes in reactive transport in porous media are ubiquitous in a multitude of contexts within the field of Earth sciences. In particular, the dynamic feedback between the reactive precipitation / dissolution processes and the solute transport, capable of giving rise to the emergence of preferential flow paths in the porous host matrix, is critical to a variety of Earth science scenarios, although the approaches to its characterization remain disputed. It has been shown that the emergence of preferential flow paths can be considered a manifestation of transport self-organization in porous media, as they create spatial gradients that distance the system from the state of perfect mixing and allow for a faster and more efficient fluid transport through the host matrix. To investigate the dynamic feedback between the transport and the reactive process in the field and its influence on the emergence of transport self-organization, we apply a reactive precipitation-dissolution Lagrangian particle tracking on a homogeneous porous matrix, composed of a calcite mineral. Subsequently, we employ Shannon entropy to quantify the emergence of self-organization in the field, which we define as a relative reduction in entropy, compared to its maximum value. Our findings show that transport self-organization in an initially homogeneous field increases with time, along with the emergence of the field heterogeneity due to the interplay between transport and reactive process, which is acerbated as the Peclet number reduces, making it diffusion-dominated. The explanation for this lies in the fact that in a completely homogeneous field, the dominant mechanism to drive reactive components out of equilibrium is the stochasticity of diffusion. The self-organization of the breakthrough curve exhibits the opposite tendencies, that are explained from the thermodynamic perspective. The hydraulic power, required to maintain the driving head pressure difference between inlet and outlet, increases with the increasing variance of the hydraulic conductivity in the field due to the evolution of the reactive process in the field. This increase in power, supplied to the fluid traveling in the porous medium, results in an increase in the level of transport self-organization in the medium.

Scaling Elastic and Plastic Deformation with Porous Media Permeability During Pressurized Flow

Shaimaa Sulieman

Drilling geothermal energy, CO2 sequestration, and wastewater injection all involve the pressurized flow of fluids through porous rock, which can cause deformation and fracture of the material. Despite the widespread use of these industrial methods, there is a lack of experimental data on the connection between the pore pressure rise, the deformation, and permeability changes in real rock. In order to address this gap in the literature, this study developed an artificial rock material that can be deformed and fractured at low pressures. Controlling the porosity, permeability, and strength of the material during the sintering process makes it possible to mimic various rock types. The artificial rock was then immersed in a liquid with the same refractive index, allowing for deformation tracking. By monitoring the flux and driving pressure and calculating the permeability changes under various pressure conditions, the study is able to examine the impact of permeability on material deformation during pressurized flow. The results show that high permeability resulted only in elastic deformation, and as the permeability decreased, the deformation became more plastic. This study provides a link between pressurized flow, rock formation permeability, and deformation that can constrain risk assessment to geothermal energy and CO2 sequestration.

Multiphase flow in porous media

When we are brewing coffee in a peculator we are actually extracting soluble oil from the ground beans. At first, the pushing water does not reach all the coffee grinds but rather they flow in a small area of the grinds. In time they will expand and extract the rest of the oil. We are interested at these long time scales where one phase replaces the other, and it has important implication not just for our morning coffee but also for CO2 sequestration and to your oil price at your gas station.

Surfactants, oil, and jumps!

Surfactants keep us clean since they are the ingredient in every soap and detergent, but they are naturally occurring in every natural system. Surfactants are molecules with hydrophobic and hydrophilic ends, and as such they are abundant in water-oil interfaces, effectively reducing the interfacial tension between them. Are they uniform in these interfaces? What influence them? These questions are not only relevant to our hygiene but also fundamental for multiphase flow in porous media since they control these marvels capillary instability known as Haines jumps.

Reactive transport

Groundwater makes the majority of accessible fresh water in the world, yet we do a poor job in keeping them fresh. While anthropogenic pollution contaminants them, over-pumping from coastal aquifers salinize them due to seawater intrusions. During these processes, the contaminations and saline water react with the fresh water in unforeseen ways. We aim to understand the physical aspects behind the mixing and reaction in this process.

The fracturing of porous media and how it may lead to earthquakes.

On September 3, 2016, a 5.8 magnitude earthquake occurred near Pawnee, Oklahoma. It wasn’t the first earthquake but the strongest one. Evidence shows that the source of these earthquakes in Oklahoma is anthropogenic. Welcome to the fascinating world of induced seismicity where burial of wastewater from oil production in one spot leads to an earthquake more than a kilometer away. This happens since the access pressure doesn’t advance uniformly, it percolates and even fractures the porous material in its way to a pre-existing fault.

In the movie, you can see a lab experiment where another liquid replaces the fluid in a brittle, porous media, zooming in with a microscope we can see beads separating and fracturing. Therefore, it seems that the fluid is fracturing its way to the fault!

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